The disclosure relates to heat assisted magnetic recording (HAMR), and particularly to alignment features and assembly methods to improve placement accuracy of a laser Chip-On-Submount Assembly (COSA) on a magnetic recording write head assembly.
Information storage devices are used to retrieve and/or store data in computers and other consumer electronics devices. Energy assisted magnetic recording (EAMR) or heat assisted magnetic recording (HAMR) technology may be used to increase areal density (AD) of hard disks.
Heat assisted magnetic recording technology requires a laser source to provide additional energy during the data writing process. The energy source normally comes from a semiconductor laser diode chip bonded on a submount assembly which is referred to as the Chip-On-Submount-Assembly (COSA). The COSA is attached to the back of a conventional magnetic head slider and the light energy from the laser diode chip is guided to an air bearing surface (ABS) through a waveguide to heat up the magnetic media. Heat from the laser beam lowers the coercivity of the magnetic medium and enables a write pole to magnetize the media with high density, which helps to realize the magnetic recording process with increased AD.
Efficient coupling of the laser beam with the optical waveguide enables writing data at high density to the disk. A requirement for bonding the COSA to the slider is the accuracy which must be achieved, typically at a submicron level. Accurate bonding helps to ensure that the output of the laser diode is aligned to the entry point of the waveguide attached to the slider. The alignment accuracy defines the amount of energy channeled into the waveguide and therefore an efficiency of the whole assembly. When the alignment is poor, more energy is needed from the laser diode to ensure sufficient energy is channeled through the waveguide. Poor alignment leads to low energy efficiency and potential degradation of laser life due to higher required output.
Another aspect impacting efficiency of light coupling into the waveguide is the distance or gap between the laser diode and the waveguide entry point. Due to the large divergence angle of the laser beam, it is desirable to have a gap between the laser diode and slider. However, conventional methods of bonding the COSA to the slider while leaving a gap between the laser diode lead to several problems. For example, the laser diode may crash into the slider during the bonding or the COSA may tilt relative to the slider thereby causing a misalignment between the laser diode and the waveguide.
Thus, there is a need in the art for methods and apparatuses to facilitate alignment of the laser COSA with the optical waveguide and avoiding crashing of a laser diode with the slider.